Cobalt fluorocarbenes: cycloaddition reactions with tetrafluoroethylene and reactivity of the perfluorometallacyclic products.

Cobalt fluorocarbene complexes CpCo(═CFR(F))(PPh2Me) (Cp = η(5)-C5H5, R(F) = F or CF3) react with tetrafluoroethylene to give the metallacyclobutanes CpCo(κ(2)-CFR(F)CF2CF2-)(PPh2Me) in the first examples of cycloaddition reactions between perfluoroalkenes and metal perfluorocarbenes. The metallacyclic products undergo a variety of reactions upon activation of the C-F bonds, including Brønsted acid-catalyzed C-F/Co-C scrambling. Implications for metal-catalyzed metathesis and polymerization of perfluoroalkenes are discussed.